Could a mixture be made up of only elements and no compounds?
To a first approximation, the air we breathe is precisely such a mixture (of course there is some carbon dioxide but it's mostly dinitrogen and dioxygen). I could dissolve alkali metals up in mercury to give amalgams - again, this is an elemental mixture. And of course there are alloys (I should have thought of this first!); these are mixtures of metals in various proportions to give metals with different properties: i.e. bronze, steel, brass.